Since the mid-1980s, many researchers had been wishing to realize a universal wireless communication system using 3G wireless communication technology. Over the years, however, not only the universal wireless communication system remains unaccomplished, but a diversity of new communication standards has derived to satisfy actual applications based on various transmission rates and transmission distances. Among the numerous communication standards, some coexist at a same region, or transmit data using same frequency bands. For example, current prevailing Bluetooth and WiFi transmit and receive data using the 2.4 GHz band.
It is known to communication management organization of many countries that, a majority of wireless frequency bands is not at all effectively utilized although there are such numerous communication standards. For instance, most mobile phone networks world-wide are constantly fully loaded, while frequency bands used by amateur radio such as walkie-talkies are rather barely occupied. To promote overall usage efficiency of radio frequency bands, it is necessary to develop a mobile device that is compatible with multiple communication standards as well as being capable of flexibly employing various frequency bands.
Unlicensed Mobile Access (UMA) is a technology which allows seamless roaming of dual mode mobile phones between local area networks and wide area networks. The local area networks may be provided by private Bluetooth networks or 802.11 networks, and the local area networks may be Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS) or Universal Mobile Telecommunication System (UMTS) mobile phone networks. The UMA technology has effectuated the concept of a wireless communication system using multiple standards and various frequency bands.
Software-Defined Radio (SDR) is regarded as a means of UMA. A fundamental principle of SDR is that, system parameters of processor platform are adjusted to achieve a single platform compatible with multiple communication standards. The processor may be a digital signal processor that generally performs transmission and reception of a physical layer.
Cognitive radio is an extension of SDR. To be more precise, cognitive radio is capable of detecting conditions such as frequency band utilization in a communication environment, and employs a reconfigurable transceiver to facilitate a mobile device to adopt appropriate communication and network capabilities. Having potentials of fully utilizing frequency bands, cognitive radio is considered as a key technique in the realm of wireless communication.
Up to the current day, technical literature on cognitive radio is mostly associated with complicated military applications, or focuses on cognitive radio concepts, simulation tools and fundamental restrictions. Further, most related researches are targeted at cognitive radio that has the ability for sensing spectrum, and more particularly, sensing spectrum of television frequency bands. According to the theory of radio, an unlicensed user is permitted to use a licensed frequency band provided that the unlicensed user does not cause any interference. However, when the licensed user comes forth, the unlicensed user is immediately blocked from that frequency band. Cognitive radio that has the ability for sensing spectrum first needs to find currently available frequency bands, followed by selecting a most suitable available frequency band satisfying the user's communication requirements. For spectrum-sensing cognitive radio, it is a vital issue as how to maintain seamless roaming while providing appropriate spectrum utilization plans.
Compared to prior art, cognitive radio having the ability for sensing spectrum indeed contributes much to frequency band utilization efficiency. However, even more versatile cognitive radio still stands as a chief development goal in the realm of wireless communication. Therefore, it is one object of the invention to provide a co-existing multi-radio system and a method of establishing the co-existing multi-radio system, in that the co-existing multi-radio system effectuates a concept of all-round cognitive radio and satisfies requirements of various communication applications.